Familial aggregation of ovarian, testicular, breast, and colorectal cancers has been identified in case reports and in epidemiologic studies. In addition, ovarian cancer risk is increased among women whose relatives have experienced breast cancer. Benign ovarian tumors are suspected of being precursors to, and sharing risk factors with, ovarian cancer. To date, no studies have investigated the occurrence of cancer in family members of women with benign ovarian tumors. A large case-control study of benign ovarian tumors is underway, and information regarding cancer among first degree relatives is being collected in that study. In the proposed study we will identify subjects from the ongoing case- control study who report a family history of ovarian, testicular, breast, and colorectal cancer, as well as subjects who report the occurrence of benign ovarian tumors and cryptorchidism. Subjects will be reinterviewed and relatives contacted in order to validate all reported diagnoses. We estimate that up to 40% of the 1000 cases and 500 controls in that study will report a positive family history of these conditions. Examination of preliminary data suggests an increased risk of testicular and ovarian cancer among first degree relatives of cases in comparison to general population rates. Valid estimation of these possible associations requires verification of the reported diagnoses. The proposed study will have excellent statistical power to estimate precisely even modest associations. The identification of any associations between benign ovarian tumors and the above cancers will add to our emerging understanding of the genetic component of cancer risk, and may stimulate the use of tissue from women with benign tumors in genetic studies. If benign ovarian tumors prove to be strongly associated with gonadal cancers, the possibility of identifying individuals and families at high risk of these cancers will be improved.